As for room size, its maybe so you have more room to dodge? At high cinder the double/triple enchanted rooms can be extremely hard but it doesnt seem worth to invest a point for such an unmeasurably small return
I agree with most of your takes, I personally like the minigames and the enchantment side, its helped me get further along a few times when I was playing like crap :P To me the Mastery Tree seem somewhat balanced, taking the bad stuff to get to the good stuff does make it feel like I've 'suffered' to get what I want. The Mimic Masteries is definitely next point spend ________ | 👀 | |_____|
